Wing case for air foils

ABSTRACT

Wing case for air foils with a closed profile shell of laminated plastic reenforced preferably by boron fibers with different orientation; flanged bars as spars sandwich the shell at corners and being bonded thereto. Aluminum ribs are in the shell, the spars are preferably made of titanium, the numbers of lamina with fiber orientations in direction of wing span and ribs correspond to the differences in elastic properties of the two metals used for ribs and spars.

United States Patent [191 Nussbaum et a1.

Mar. 2, 1971 Assignee:

Filed:

Appl. No.: 230,236

WING CASE FOR AIR FOILS Inventors: Helmut Nussbaum, Bremen; HilmarSchnell, Delmenhorst, both of Germany Vereinigte FlugtechnischeWerke-Fokker GmbI-I, Bremen,

Germany Feb. 29, 1972 Foreign Application Priority Data References CitedUNITED STATES PATENTS 12/1932 Messerschmitt 244/123 Germany P21 US. Cl.244/123 Int. Cl. B64c 3/20, B64c 3/26 Field of Search 244/123, 124;

[ Dec. 25, 1973 2,901,455 8/1959 Jurras 161/59 FOREIGN PATENTS ORAPPLICATIONS 2,032,283 3/1971 Germany 244/123 Primary Examiner-George E.A. Halvosa Assistant Examiner-Charles E. Frankfort Attorney-Ralf H.Siegemund [5 7] ABSTRACT Wing case for air foils with a closed profileshell of laminated plastic reenforced preferably by boron fibers withdifierent orientation; flanged bars as spars sandwich the shell atcorners and being bonded thereto. Aluminum ribs are in the shell, thespars are preferably made of titanium, the numbers of lamina with fiberorientations in direction of wing span and ribs correspond to thedifferences in elastic properties of the two metals used for ribs andspars.

3 Claims, 4 Drawing Figures WING CASE FOR AIR FOILS The presentinvention relates to a wing case for air foils, and here particularly tothe composite construction of such a case which includes metal fiberreenforced material. I

It is known generally to make parts of an aircraft from fiber-reenforcedlaminated material. This material is used for some of those componentswhich have to have great strenght and rigidity. Particularly, ruddershave been constructed for test purposes from plastic which is reenforcedby boron fibers. The rudder was particularly constructed underutilization of the so called sandwich construction principle, wherein aconventional titanium frame is covered with such plastic sheathinghaving boron fibers for reenforcement and being of laminatedconstruction. Such boron fiber reenforced plastic in sandwichconstruction has been tentatively used also in other portions of anaircraft.

These various contemplated and actual uses of such fiber reenforcedplastic is directed only toward a mere substitute or replacement formetal shell parts and sheathing. It has not been taken intoconsideration that the physical properties of these sheaths, such,aselastic moduli and coefficient of thermal expansion are variable overwide ranges and can be made to depend on fiber orientation andcombination. It is an object of the present invention to provide fiberreenforced laminated plastic sheathing that is constructed in particularrelation to the metal parts used in addition and in composite,structural configuration with the sheathing. Considering particularlythe construction of a wing case in an aircraft, the overall constructionis to take into consideration that fiber reenforced laminated plasticsheathing as anisotropic properties; fiber technology and the physicalproperties of the metal parts as they are to be used in the compositeconstruction are to be mutually optimised.

In accordance with the preferred embodiment of the present invention, awing case to to be constructed as follows. A shell is to be made ofclosed profile in cross section, using fiber reenforced laminatedplastic sheathing (matrix material) to serve as top and bottom of thewing case as well as web of spar. Particularly, profiled metal bars arebonded to the shell to serve as spar flanges whereby such a spar flangeequivalent is divided into inner and outer flanges, innerandouterunderstood in relation to the closed shell. The ribs in the wing are tobe made of metal. Ribs and bars serving spar flanges may be made fromdifferent metals (e.g., aluminum and titanium respectively).Accordingly, the modules of elasticity of the shell in wing spandirection and transversely thereto are matched to the correspondingmodules of these metal parts. For this, the lamina of different fiberorientation are selected in number so as to obtain the desired relativeelastic moduli in the different directions.

Additional lamina with obliquely transverse fiber orientation may beprovided to obtain more graduated transition in the several propertiesas far as change with direction is concerned. 7

For aluminum ribs and titanium spars and boron'fiber reenforced plastic,the numbers of lamina used should be related as follows. Some laminahave their fibers oriented in direction of extension of the spars orwing span (called the orientation). Others have their fibersoriented atright angles thereto, i.e., in direction of the ribs (called the 90orientation). Still others have their boron fibers oriented at 45 or 45to either direction. Let the number of layers be respectively t I90.these numbers should be related by under the additional assumption thatthe laminated sheathing is layered symmetrical to a center plane. Thetotal number of layers, having their reenforcing fibers oriented inparticular direction, is, of course, the equivalent of the relativethickness of fiber-laminate in the sheathing with fibers oriented inthat direction, because all layers or lamina are deemed to have similarthickness.

It should be noted that such fiber reenforced plastic sheathing is quiteexpensive, but a composite construction as suggested here permits arelative weight reduction by 30 percent which more than offsets the highcost of the material. Also, a wing constructed in that manner permitsalmost completely undisturbed uniform thrust drop off in the closedshell, making full use of fiber technology, particularly as to forcedistribution and force transmission between wing case and connectingstructure. I While the specification concludes with claims particularlypointing out and distinctly claiming the subject matter which isregarded as the invention, it is believed that the invention, theobjects and features of the invention and further objects, features andadvantages thereof will be better understood from the followingdescription taken in connection with the accompanying drawings in which:

FIG. 1 illustrates schematically a section view through a wing, showingthe principle arrangement of parts in accordance with the invention:

FIG. 2 illustrates a perspective view of the wing case of FIG. 1,showing greater detail of the relevant components involved;

FIG. 3 shows a section through spar construction for connecting theleading edge construction of the wing to the wing case, using a combinedfriction and positive lock; and

FIG. 4 shows modified connection of wing nose to wing case by means ofbolting.

Proceeding now to the detailed description of the drawings, FIGS. 1 and2 illustrate the shell construction of the body of a wing or wing case.Reference numeral 1 refers to the shell which is composed of laminated,fiber-reenforced material. Plural layers of lamina are included in asheet wherein the individual layers differ as to fiber orientationincluding particularly transversely oriented layers and lamina (matrixmaterial). The spar flanges for the wing case are constructed underutilization of particularly profiled bars made of titanium. These sparflanges are arranged in pairs (20, 2b) to sandwich and to curve theshell. Each divided spar is thus comprised of an inner flanged bar 20and an outer flanged bar 2b, having shell I sandwiched in between. Theterms inner and outer relate here to the section profile of the shell asa whole.

The spar structure provided for the transition of the wing or air foiltop and bottom portions la of the shell to the portion lb thatconstitute parts of the web of spar structure. Each outer flanged sparmay be divided additionally, depending upon the connecting structure forthe wing. As shown in FIG. 2, ribs 3 can be provided inside of shell 1;the ribs are usually made from material different from the material ofthe flanged spars (e.g., aluminum).

The area A in FIG. 2 refers particularly to a more detailed illustrationof the fiber orientation within the several lamina of shell 1. Somemetal fibers in their respective plastic lamina extend in direction X(called 0- rlentation for the fibers), which is the direction of thespan of the wing and of the spar structure accordingly. Other fibersextend in direction Y (called 90 orientation), which defines theextension of the ribs. Additional layers have their fibers oriented at45 to the X and Y axes as defined, and still further layers have theirfibers oriented at 90 thereto (i.e., 45 to the X/Y axes as defined).

Assuming that titanium is used for the several spars 2a and 2b, andassuming further that ribs 3 are made of aluminum, a rule should beobserved according to which the number t of lamina in shell 1 with 0fiber orientation is to be twice as large as the number 2 of layers andlamina with 90 fiber orientation. The total number 1 of layers with i 45fiber orientation should correspond to the number of layers with 0 fiberorientation. In other words, the relationship to r90 r 2 z 1 2 should beobserved upon construction the sheathing that will constitute shell 1.

FIG. 3 shows a first example for the divided structure for the sparflanges as establishing the transition between shell portion la to theshell portion lb that constittites part of the web of spar structure.The spar flanges in particular are constructed for releasable frictionalform, closed and flush connection of wing case shell 1 to the wingstructure that establishes the leading edge, nose box or case 4. Thenose case 4 is provided as a releasable unit, just as the end casesusually are. The inner flanged bar 2a of the spar flange, as well as aportion of the outer flanged bar of the spar flange, are bonded toshell 1. In accordance with the definition of terms inner and outer, areleasable cover 2d pertains to the outer spar portion and is bolted tothat outer spar 2c. Cover 2d provides for smooth contour transition asbetween, e.g., wing case top and the upper part of the nose case thatbecomes the leading edge. Cover 2d, as so combined with bar 20, providespositive connection between nose case 4 and the laminated shell 1. Case4 itself may also be of composite construction.

FIG. 4 illustrates a different tri-parted spar construction, includinginner spar 2a as before, strap or cover plate 2f and flanged bar orouter spar flange 2e. The shell 4 for the leading edge of the wing isbolted between the releasable plate or cover 2f and the flanged bar 2ewhich, in turn, is bonded to shell 1. Inner spar flange 2a is alsobonded to shell 1 as before, and may be rivetedor bolted additionally toouter spar flange 22.

The web of spars -1b may actually be completely enclosed by inner andouter spar flanges. In other words, top and bottom spar flanges mayactually be combined, but in pairs so as to establish inner and outerspar flanges in relation to shell 1, each traversing the thicknessdimension of the wing in its entirety, if that dimension is relativelysmall. The wing case can be manufactured in accordance with thefollowing procedures.

A dummy core is made to have outer contour matching the inner contour ofthe shell to be made. Next, layer upon layer is disposed thereon, usingso-called Preprej-tapes or winding single thread or other tapes offiber-reenforced material thereon, until a completely closed laminatedshell has been constructed. Upon providing the laminated structure, therules for fiber orientation can readily be observed. The core may be ofcollapsible construction, holding also the ribs 3 and the inner sparflanges 2a, so as to establish their position relative to the case.

As the fiber-reenforced material cures the ribs and the several sparflanges are bonded to top and bottom shell portions. After removing thecollapsible supporting core structure, a tubular case has been made thatincludes all of the internal components for such a wing shell withspars. Further working may proceed from the outside.

In accordance with another manufacturing method, pressure is employed. A(somewhat smaller) core is covered with an inflatable shell made from athin foil. The inner spar flanges are disposed in proper position onthat shell. Next, the fiber reenforced material as described is placedthereon to obtain the laminated structure that will ultimatelyconstitute shell 1. The fibers in the several lamina as so disposed havethe required orientation. Next, the entire structure as made thus far isplaced into a mold structure whose contour is the complement or negativeprofile of the wing case to be made. Now, the inflatable shell isinflated by feeding pressurized air into space between that shell andthe core. The pressure as so applied is instrumental in curing theplastic, whereby concurrently the inner spar flanges are bonded toshell 1. The ribs 3 are bonded to the interior of the shell afterremoving core and inflatable shell, through the open front ends of thewing case. The bonding pressure needed here is locally applied, usingtooling that works also on the principle of inflation to obtain therequired pressure force acting on the parts to be bonded.

The invention is not limited to the embodiments described above but allchanges and modifications thereof not constituting departures from thespirit and scope of the invention are inteded to be included.

I claim:

1. Wing case for air foils, comprising:

a shell of closed profile in cross section made of laminated plastic,reenforced by fibers oriented in a first plurality of lamina indirection of the wing span, the fibers being oriented differently in asecond plurality of lamina, the shell establishing top and bottomportions of the wing as well as webs or spar;

a plurality of flanged metal bars as spar flanges arranged in pairsinside and outside of the shell and being bonded thereto; and

metal ribs disposed inside of the shell, wherein different metals areused for the ribs and the bars, the fibers in the second plurality oflamina being oriented in direction of the ribs, the number oflamina ofthe first plurality with fibers oriented in direction of the wing spandiffers from the number of lamina of the second plurality with fibersoriented in direction of the ribs so that the modules of elasticitythereof in the directions of the wing span and of the ribs differcorrespondingly to the differences in modules of elasticity of the twometals.

2. Wing case as in claim 1, there being a third plurality of laminahaving their fibers oriented at i45 to either said directions.

3. Wing case as in claim 2, wherein the shell is constructed of laminawith boron fiber reenforced plastic, the bars made of titanium, the ribsmade of aluminum, the numbers of layers of said first, second and thirdpluralities of lamina related by 2 l 2.

1. Wing case for air foils, comprising: a shell of closed profile incross section made of laminated plastic, reenforced by fibers orientedin a first plurality of lamina in direction of the wing span, the fibersbeing oriented differently in a second plurality of lamina, the shellestablishing top and bottom portions of the wing as well as webs orspar; a plurality of flanged metal bars as spar flanges arranged inpairs inside and outside of the shell and being bonded thereto; andmetal ribs disposed inside of the shell, wherein different metals areused for the ribs and the bars, the fibers in the second plurality oflamina being oriented in direction of the ribs, the number of lamina ofthe first plurality with fibers oriented in direction of the wing spandiffers from the number of lamina of the second plurality with fibersoriented in direction of the ribs so that the modules of elasticitythereof in the directions of the wing span and of the ribs differcorrespondingly to the differences in modules of elasticity of the twometals.
 2. Wing case as in claim 1, there being a third plurality oflamina having their fibers oriented at + or - 45* to either saiddirections.
 3. Wing case as in claim 2, wherein the shell is constructedof lamina with boron fiber reenforced plastic, the bars made oftitanium, the ribs made of aluminum, the numbers of layers of saidfirst, second and third pluralities of lamina related by 2 : 1 : 2.